KeyPair::from_pem detects incorrect algorithm?

How to reproduce

Test certificates

Working certificates (-sha256 option)

openssl req -x509 \
                        -sha256 -days 356 \
                        -nodes \
                        -newkey rsa:4096 \
                        -subj "/CN=example.com" \
                        -keyout rootCA.key -out rootCA.crt

Failing certificates (-sha512 option)

openssl req -x509 \
                        -sha512 -days 356 \
                        -nodes \
                        -newkey rsa:4096 \
                        -subj "/CN=example.com" \
                        -keyout rootCA.key -out rootCA.crt

Code

use std::fs::read_to_string;

fn main() {
    let private_key = read_to_string("rootCA.key").unwrap();
    let private_key = rcgen::KeyPair::from_pem(&private_key).unwrap();
    println!("KeyPair alg: {:?}", private_key.algorithm());

    let cert = read_to_string("rootCA.crt").unwrap();
    let params = rcgen::CertificateParams::from_ca_cert_pem(&cert, private_key).unwrap();

    println!("Params alg: {:?}", params.alg);

    if let Err(e) = rcgen::Certificate::from_params(params) {
        println!("Error: {:#}", e);
    } else {
        println!("All good :-)")
    };
}

Test results

If using the -sha256 certificate files, the output is:

KeyPair alg: PKCS_RSA_SHA256
Params alg: PKCS_RSA_SHA256
All good :-)

If using the -sha512 certificate files, the output is:

KeyPair alg: PKCS_RSA_SHA256
Params alg: PKCS_RSA_SHA512
Error: The provided certificate's signature algorithm is incompatible with the given key pair

Is this expected?

Reproduce the issue with the supplied OpenSSL commands and Rust example, then inspect KeyPair::from_pem and CertificateParams::from_ca_cert_pem to compare the SHA-256 and SHA-512 algorithm values. Done means establishing whether the differing algorithms are expected and documenting or covering the correct compatibility behavior.